1. Field of the Invention
The present invention relates generally to drug delivery devices, and more particularly to devices for storing, transporting and dissolving dry reagents.
2. Description of the Related Art
Medical treatments often involve solutions or suspensions of drugs or other reagents to be injected into the human body. Mixing and injecting such solutions can be extremely expensive and inaccurate. Thus, there are a number of problems with current methods of intravenous drug delivery.
Conventional methods involve administration of drug solutions derived from thawed preparations of previously frozen drug solutions or from drug solutions produced by connection of a diluent pouch with a drug-containing vial. The later delivery method requires considerable manipulation to place the dry drug formulation into solution prior to administration to the patient. Among the greatest problems associated with existing methods are the direct and indirect costs of the delivery systems. For frozen solutions indirect costs are associated with freezers, temperature monitoring equipment and procedures required to maintain drug supplies. Direct costs are associated with the labor required to thaw the frozen solutions prior to administration to the patient. Similarly, for preparation of drug solutions using dry drug and separate diluent preparations, costs are associated with the requirement for multiple components and the manipulation required to place the drug in solution.
The requirement for freezing drug solutions or use of multiple components to prepare drug solutions results from the instability of many drugs once the drugs are activated or placed into solution. Over time, sometimes within a matter of 1 to 2 hours, the efficacy of drugs diminishes after they are placed in solution. Accordingly, additional costs are associated with the waste associated with formation of drug solutions that are not administered to the patient in a timely manner, for example, when changes in prescription or patient movement preclude administration of the prepared drug solution.
The manipulation associated with combining a separate drug vial and a diluent from a pouch includes threading of a separate drug-containing vial into a threaded receptacle. Inadequate threading together of these components results in leakage of the diluent or drug solution from this junction and breaches the sterile barrier intended to be formed between the drug vial and the diluent pouch. The repeated effort required to thread these separate components together has lead to carpal tunnel syndrome among healthcare providers. For certain delivery systems, an internal cork must be removed by manipulation through the walls for the diluent pouch in order to expose the dry drug within the vial to the diluent. Omission of this step results in administration of diluent without drug to the patient.
Moreover, in order to properly dissolve the drug in the diluent the combination of components must be vigorously agitated. It is often not possible to be absolutely certain that all the drug has been removed from the vial. Because of the translucent nature of the diluent pouch, it is also sometimes difficult to differentiate between dissolved drug and minute, undissolved drug particles within the diluent pouch. If undissolved drug particles are administered to patients they present a serious potential hazard to the patient of an embolus capable of occluding small blood vessels.
Administration of the additional fluids required for administration of drug solutions using a secondary set of fluids, beyond those administered to maintain electrolyte balance, results in fluid problems in patients with fluid retention maladies.
The volume occupied by existing delivery systems and/or the requirement for maintaining a frozen environment prevents these systems from being used in automated dispensing devices.
An alternative to use of these delivery systems is the preparation of drug solutions by pharmaceutical personnel from bulk containers of drug. These procedures require a considerable amount of effort by these personnel and represents a serious hazard to the pharmacy and drug administration personnel due to the toxicity of some agents.
U.S. Pat. No. 5,259,954 to Taylor, issued Nov. 9, 1993 (hereinafter xe2x80x9cthe ""954 patentxe2x80x9d) and U.S. Pat. No. 5,725,777 issued Mar. 10, 1998 (hereinafter xe2x80x9cthe ""777 patentxe2x80x9d) disclose a drug pack or xe2x80x9creagent modulexe2x80x9d suitable for storing dry reagents and for preparing solutions for administration by passing fluid through the pack. These references are incorporated herein by reference. The ""777 patent discloses two embodiments in which a porous compression element constantly exerts an inward force on a dry reagent bed, keeping it compacted even as the bed is eroded by passing fluid through the porous compression element and through the bed. This arrangement advantageously enables efficient uniform dissolution of the reagent bed by avoiding channel formation through the reagent bed.
While the reagent modules of the ""954 and ""777 patents operate well in storing and dissolving reagent beds efficiently, there remains room for improvement.
An in-line drug delivery pack that connects in-line with an intravenous (IV) line and allows for the mixing of diluent with a drug reagent to be delivered to the patient. An internal drug bed bypass mechanism is tailored to apportion diluent flow between the bypass and the drug bed. The apportionment is selected to achieve a solution concentration suitable for IV administration as the dried reagent is dissolved.
Thus, both dissolution and precisely tailored dilution are performed in the same simple device.